1. Field of the Invention
The present invention relates to a drive mechanism for a camera, such as an AF mechanism or a camera shake correction mechanism.
2. Description of the Related Art
In an example of a known AF mechanism of a digital camera, a CCD (image pickup device) is moved in an optical axis direction in accordance with contrast information of image data of an object image picked-up by the CCD, so that the image light transmitted through a photographing lens is always converged onto an image pickup surface of the CCD (e.g., Japanese Unexamined Patent Publication No. 8-154196).
In this AF mechanisms a driving device is used as an electromagnetic drive device to move the CCD in the optical axis direction. Specifically, a permanent magnet is provided on the camera body side, a substantially cylindrical yoke is provided on the camera body side and which is located inside the permanent magnet, and a cylindrical voice coil is provided on a support which supports the CCD and which is located in a cylindrical space defined between the permanent magnet and the yoke, and coaxial to the yoke.
A CPU (Central processing Unit) incorporated in the digital camera supplies a predetermined amount of electric current to the voice coil for a predetermined period of time, while controlling the direction thereof, in accordance with contrast information of data of an object image picked-up by the CCD. Consequently, the CCD is linearly moved by a predetermined amount in the optical axis direction so that the image light transmitted through the photographing lens is converged onto the image pickup surface.
Since the voice coil and the yoke, that constitute the electromagnetic drive device used in Japanese Unexamined Patent Publication No. 8-154196, are cylindrical in shape, the size of the electromagnetic drive device is large in the optical axis direction (forward/backward direction) and in the upward/downward direction and right/left direction, perpendicular to the optical axis direction. Moreover, if the drive force of the electromagnetic drive device is increased so as to achieve a high-speed AF operation, the size of the voice coil and the yoke is increased in the optical axis direction and directions orthogonal thereto. Under these circumstances, it is difficult to miniaturize the digital camera if the electromagnetic drive device is used,
Furthermore, the voice coil which is large in size, is also heavy. Therefore, it is difficult to move a support which holds the voice coil at a high speed. In order to move the support at a high speed, it is necessary to increase the power consumption. Also, the manufacturing cost of the cylindrical voice coil is high.